1. Field of the Invention
The present invention relates to a vibrating gyroscope, and more particularly to a vibrating gyroscope used in a video camera or the like to detect external vibrations such as hand shaking by detecting a rotational angular velocity and cancel out the vibrations on the basis of the detected information. The invention also relates to a method for adjusting the above type of vibrating gyroscope.
2. Description of the Related Art
FIG. 18 is a perspective view of an example of a conventional vibrating gyroscope. This vibrating gyroscope 100 comprises a vibrator 101 of a substantially regular triangle bar shape. The vibrator 101 is composed of a vibrating body 102 of a substantially regular triangle bar shape made up of a permanently elastic metal and piezoelectric elements 103a, 103b, and 103c which are substantially rectangular in shape and which are attached nearly in the center of each of the three side surfaces of the vibrating body 102.
The piezoelectric element 103c is used for input of a drive signal, and the piezoelectric elements 103a and 103b are used for detection and feedback. On both surfaces of each of the piezoelectric elements 103a, 103b, and 103c electrodes (not shown) are formed, and one of them is joined to the vibrating body 102 and the other electrode is connected to one end of the lead wires 106a, 106b, and 106c by soldering, etc. The ends of the lead wires 106a, 106b, and 106c which extend to the vicinity of the nodal point of the vibrating body 102 are fixed thereto using elastic adhesive 107, and the other end of the lead wires 106a, 106b, and 106c are led to the surface of the mounting base 105 and connected to a circuit (not shown).
Also, in the vicinity of nodal points in the first order vibration mode on the edge line portion 102d of the vibrating body 102 of the vibrator 101, metallic support members 104 and 104 having the shape of a square letter "C" made up of a thin wire of a high elasticity are joined by, for example, soldering. And the end portions of the support members 104, 104 are joined to one main surface of the mounting base 105 made up of glass epoxy material, etc., and the vibrating body 10 is supported by the mounting base 105 through the support members 104, 104.
And although not particularly shown, between the piezoelectric element 103c for input of a drive signal and the piezoelectric elements 103a and 103b for detection and feedback, a drive circuit as a feedback loop for self-oscillation of the vibrating body 102 is connected, and because of this drive circuit the vibrator 102 generates bending vibration at a right angle to the surface on which the piezoelectric element 103c is provided. This bending vibration is hereinafter referred to as a drive mode (fx mode). While the bending vibration in the drive mode is generated, bending vibration in the direction perpendicular to the drive mode is induced owing to the Coriolis force when the rotation around the axis of the vibrating body 102 is added. This bending vibration is called a detection mode (fy mode) in the following explanation. The bending vibration in the detection mode causes an output difference between the piezoelectric elements 103a and 103b proportional to the angular velocity, and the angular velocity can be detected by detecting the output difference using a detection circuit.
In the conventional vibrating gyroscope 100, there has arisen the problem that the vibration of the vibrator 101 leaks to the mounting base 105 through the four legs of the support members 104, 104. In addition, when the change of external conditions such as impact, vibration, temperature change, etc. affects the vibrating gyroscope 100, the leakage of the vibration from the four legs of the support members 104, 104 is different. This causes the vibration of the vibrator 101 to become unbalanced in such a way that it becomes difficult to detect an accurate angular velocity. Also, there arises another problem in that the vibrating gyroscope 100 has had a weakness at impact because the support members 104, 104 are formed using a thin wire material.
In addition, the vibrating gyroscope shown in FIG. 18 has a problem that the sensitivity of detecting angular velocity is greatly varied as shown in a graph of FIG. 21 when the frequency characteristic (resonance characteristic) becomes different because of the change of external conditions. That is, as these vibrating gyroscopes are formed so that the resonance frequency in the fx mode coincides with the resonance frequency in the fy mode, they have a good detection sensitivity. However, because the slope of the curve showing the resonance characteristic in the fy mode is sharp, there is a concern that the detection sensitivity may be greatly changed when the resonance frequency in the fy mode corresponding to the resonance frequency in the fx mode is changed owing to the change of external conditions.
For the foregoing reasons, there is a need for a vibrating gyroscope which is hardly affected by the change of external conditions and is able to accurately detect angular velocity.